In the past, as an electric cylinder used in various kinds of apparatuses, for example, there is an electric cylinder described in Japanese Patent Application Laid-Open Publication No. 08-117970 and CN1074820C. This electric cylinder includes a piston attached to a ball nut screwed with a screw stock, a motor that controls to rotate the screw stock, a hollow rod provided on the front surface of the piston, and a supporting member inserted into a hollow portion of the hollow rod and rotatably provided at the distal end of the screw stock. Urethane rubber is attached to a rod head at the distal end of the hollow rod via an attachment plate. A metal protection plate is provided at the distal end of this urethane rubber. This electric cylinder is robust against high temperature and can weaken impact. Therefore, the electric cylinder is suitable for use in a push-out apparatus that pushes out a heavy and hot object and a receiving apparatus that receives the object.
As an electric cylinder system using an electric cylinder or the like, for example, there is an electric cylinder system described in Japanese Patent Application Laid-Open Publication No. 2005-254290. This electric cylinder system includes, as shown in FIG. 13, an electric cylinder 305 including a lifting rod 305c that rises and falls according to the rotation of a motor 305b, a load cell 306 functioning as a load detector coupled to the lifting rod 305c, a position detector (an encoder 305a) that detects the position of the lifting rod 305c, calculating means 308 electrically connected to the load cell 306, and a control section 309 electrically connected to the calculating means 308, the motor 305b, and the position detector (the encoder 305a). Further, the electric cylinder system includes a lower frame 301, a guide rod 302, an upper frame 303, a movable frame 304, a holder 304a, and a pressing member 307. The pressing member 307 is attached to the distal end of the load cell 306 and retains a work 311. On the lower frame 301, a work 312 is placed under the work 311.
In this electric cylinder system, control is performed by a method explained below. Specifically, the method includes: a step of setting pressing speed and a target load; a step of calculating, with calculating means, from the set pressing speed and target load, a speed pattern in which the pressing speed is reduced in proportion to an increase in a load and is reduced to zero when the load reaches the target load; and a step of issuing a command from a control section to a motor and actuating an electric cylinder according to the calculated speed pattern to press a work. At least one deceleration changing point is set in the speed pattern. The deceleration of the pressing speed reduced in proportion to an increase in the load is changed at the deceleration changing point.